Mankind discovers the secret of 'slipgates' called teleporters. However, they're misused by some strange force code-named 'Quake', which uses the slipgates to send hordes of warriors to earth to take over the whole world.
A marine special unit, to which you belong, is instructed to seek and kill 'Quake' and his minions - somehow 'Quake' knew about the plan and erased the whole unit - except for - surprise! - you.
You throw a round of shells into the shotgun, sharpen your axe and engage to the strange and ancient worlds of 'Quake's realm.
You learn that 'Quake' is actually Shub-Niggurath, a hideous demon and witch-goddess, and that the monsters are her breed!
You decide to collect the four runes of magic to find Shub and kick his god-forsaken ass!